1. Field of the Invention
The present invention relates to a method for manufacturing a bonded substrate, and more particularly to a method for manufacturing a bonded substrate having a silicon thin film formed on a front surface of an insulator substrate.
2. Description of the Related Art
To realize higher performances of a semiconductor device, a silicon-on-insulator (SOI) substrate has come under the spotlight in recent years. Further, a silicon-on-quartz (SOQ) substrate or a silicon-on-glass (SOG) substrate in which a support substrate (a handle wafer) is not formed of silicon is also expected to be applied to, e.g., a TFT-LCD, a radio-frequency (RF) device, or any other MEMS product.
There has been proposed a method for manufacturing, e.g., the SOQ substrate by using, e.g., a silicon substrate as a donor wafer whilst using a quartz substrate as a handle wafer and bonding these different kinds of substrates (see Japanese Patent Application Laid-open No. 2006-324530). In the thus fabricated bonded substrate, since the quartz substrate is usually fabricated by double-side polishing for simultaneously polishing a front surface and a back surface thereof, the back surface is also a mirror surface, there may occur problems in process/evaluation that are different from those of a regular SOI substrate manufactured by bonding silicon substrates.
As one of such problems, a wafer is appressed against a stage and hence becomes hard to be removed from the stage when carrying and fixing an SOQ substrate on an apparatus, or identifying a front surface and a back surface is difficult to provoke an erroneous operation in handling since a transparent substrate is adopted, for example.